Xe133 elimination from human fat during negative- and positive-pressure breathing

The elimination of Xe133 from a deposit in the subcutaneous adipose tissue outside the anterior tibial muscle was recorded by an external scintillation detector in 16 human subjects during normal breathing, negative-pressure breathing (-20 cm H2o), and positive-pressure breathing (+20 cm H2O). The ambient temperature was kept at 28.0 degrees C +/- 0.1 degrees, which can be considered a neutral temperature. The xenon clearance rate was increased during negative-pressure breathing by a mean of 68% and decreased during positive-pressure breathing by a mean of 73% when compared to normal breathing. The xenon-elimination rates during the different conditions may reflect corresponding changes in adipose-tissue blood flow. Because both negative- and positive-pressure breathing may occur during diving, the uptake and elimination of inert gases in adipose tissue of a diver may be influenced; thus, the risk of decompression sickness might also be affected. The results may therefore be of importance in diving routines and in the construction of breathing apparatus for divers.